Radio access schemes and radio networks (hereinafter referred to as a long term evolution (LTE) or an evolved universal terrestrial radio access (EUTRA)) of cellular mobile communication have been examined in the 3rd Generation Partnership Project (3GPP). In the LTE, a base station apparatus is referred to as an evolved NodeB (eNodeB) and a terminal apparatus is referred to as user equipment (UE). The LTE is a cellular communication system in which a plurality of areas covered by base station apparatuses are arranged in cell forms. A single base station apparatus may manage a plurality of cells.
The LTE may correspond to time division duplex (TDD). The LTE adopting a TDD mode is referred to as a TD-LTE or LTE TDD. The TDD is a technology for enabling full duplex communication at a signal frequency band by performing time division multiplexing on an uplink signal and a downlink signal.
The 3GPP have examined that traffic adaptation technologies and interference management and traffic adaptation (IMTA) technologies are applied to the TD-LTE. A traffic adaption technology is a technology for changing a ratio between an uplink resource and a downlink resource according to an uplink traffic and a downlink traffic. The traffic adaptation technology is also referred to as a dynamic TDD.
In NPL 1, a method of using a flexible subframe is suggested as a method of realizing traffic adaptation. A base station apparatus can receive an uplink signal or transmit a downlink signal in a flexible subframe. In NPL 1, a terminal apparatus regards a flexible subframe as a downlink subframe unless the terminal apparatus receives an indication to transmit an uplink signal in the flexible subframe from the base station apparatus.
NPL 1 discloses that a hybrid automatic repeat request (HARQ) timing with respect to a physical downlink shared channel (PDSCH) is determined based on newly introduced uplink-downlink configuration and an HARQ timing with respect to a physical uplink shared channel (PUSCH) is determined based on initial UL-DL configuration.
NPL 2 discloses that (a) UL/DL reference configuration is introduced and (b) some subframes can be scheduled for either of an uplink and a downlink via dynamic grant/assignment from a scheduler.
In section 7.2 of NPL 3, a procedure of terminal apparatuses for reporting of channel state information (CSI) is described. A base station apparatus allocates downlink resources to the terminal apparatuses based on the channel state information reported from the plurality of terminal apparatuses. The channel state information includes a channel quality indicator (CQI).